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In the connecting structure of the present invention, connectors 8 and 9
which are in contact with terminals 6 and 7 are connected to fuel cell 1
including first cells 2a which have the terminals 6 and 7 at an anode
plate and a cathode respectively, and second cells 2b which have
terminals 6 and 7 in neither an anode plate nor a cathode, stacked
alternately.

1. A connecting structure between a connecting apparatus for a fuel cell
and a fuel cell having a structure in which first cells having terminals
provided to cathodes and anodes thereof, and second cells having
terminals provides to neither cathodes nor anodes thereof are stacked in
alternation, characterized in that the connecting apparatus and the fuel
cell are electrically connected by contacting the terminals with the
connectors which are disposed at positions corresponding to the
terminals, in the connecting apparatus.

2. The connecting structure as set forth in claim 1, wherein the first
cells are disposed on at least both ends of the fuel cell, and the
connectors are connected to the fuel cell consisting of the first cells
and the second cells which are stacked alternately from both ends of the
fuel cell.

3. (canceled)

4. (canceled)

5. A fuel cell comprising: first cells provided with terminals to each of
anodes and cathodes thereof, and second cells provided with no terminals
to neither anodes nor cathodes thereof, wherein the first cells and the
second cells are stacked alternately.

6. The fuel cell as set forth in claim 5, wherein the first cells are
disposed to at least both ends in the direction of stacking, and the
first cells and the second cells are stacked alternately from both ends.

7. A fuel cell comprising: first cells provided with terminals to each of
anodes and cathodes thereof, and second cells provided with no terminals
to neither anodes nor cathodes thereof, wherein the first cells are
stacked from an end of an anode side in a stacking direction and the
second cells are stacked from an end of a cathode side in a stacking
direction, alternately.

8. The fuel cell as set forth in claim 7, wherein third cells from
neither the anodes nor cathodes of which terminal are taken out are
stacked with the first cells or the second cells alternately.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a Division of application Ser. No. 11/198259,
filed Aug. 5, 2005, which application is incorporated herein by
reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a connecting structure to a cell
of an electrical voltage detecting connector which is connected to a fuel
cell constituted by laminating plural cells having an anode and a
cathode, for detecting electrical voltage of the cell, and to a fuel
cell.

[0004] Priority is claimed on Japanese Patent Application No. 2004-235153,
filed Aug. 12, 2004, and Japanese Patent Application No. 2004-235154,
filed Aug. 12, 2004, the contents of which are incorporated herein by
reference.

[0005] 2. Description of Related Art

[0006] In recent years, fuel cells are attracting attention as a new
source of power, such as for an automobile. In general, a fuel cell
consists of a membrane electrode architecture (MEA) in which an anode
electrode (positive electrode) and a cathode electrode (negative
electrode) are disposed on either side of a solid polymer electrolyte
membrane respectively, and a pair of separators which contain the
membrane electrode architecture therebetween. When this fuel cell is
operated to generate electricity, it generates an electrochemical
reaction by supplying gaseous fuel (for example, hydrogen gas) to the
anode electrode of the fuel cell, and supplying oxidizing gas (for
example, air containing oxygen) to the cathode electrode. Since only
harmless water is generally generated when generating electrical power,
the fuel cell attracts attention from a viewpoint of influence on the
environment or use efficiency.

[0007] Incidentally, it is difficult to obtain electric power sufficient
to drive an automobile from one fuel cell. It has been investigated to
mount a fuel cell which has a stack structure in which plural cells each
of which is formed by interposing a membrane electrode architecture
between a pair of separators are layered, in an automobile, such that
sufficient electric power to drive the automobile can be supplied.

[0008] In this case, in order to monitor whether a cell which constitutes
a fuel cell is generating electricity normally, it is very important to
detect the voltage of the cell. From such a viewpoint, a fuel cell
provided with terminals for measuring voltage is proposed.

[0009] For example, patent document 1 (Japanese Unexamined Patent
Application, First Publication No. H09-283166) discloses technology in
which a circular hole is formed in the carbon plate of each cell, and one
end of an output terminal is connected to the circular hole using a
banana clip, and another end of an output terminal bundle with a voltage
measuring apparatus is connected through a connector.

[0011] Moreover, cross sections of the principal part of a fuel cell and
of a voltage detecting connector which is connected to the fuel cell are
shown in FIG. 5. As shown in this figure, a fuel cell 30 consists of a
predetermined number (in this case, n) of cells 31, which are stacked.
Each cell 31 is interposed between separators 33 and 34 in a membrane
electrode architecture 32. In each cell 31, terminals 35 and 36 for
measuring electrical voltage are disposed on the separator 33 at an anode
electrode side and the separator 34 at a cathode electrode side,
respectively. A cell connecting device 39 is connected to the fuel cell
30 thus constituted. The cell connecting device 39 is equipped with a
predetermined numbers of connectors 37 and 38, whereby the electrical
voltage of the separators 33 and 34 disposed at the terminals 35 and 36
can be detected by contacting the connectors 37 and 38 with the terminals
35 and 36, thereby, detecting electrical voltage in each cell.

[0012] However, hitherto, there were the following problems. That is, in
the conventional art, as explained above, referring to FIG. 5, in
general, each terminals 35 and 36 of the fuel cell 30 are arranged in
series in the same position when they are looked at from a direction of
layering. However, in order to mount the fuel cell 30 in a vehicle etc.,
it is required to reduce the thickness of each cell 31 to as thin as
possible, and the gap between the terminals 35 and 36 tends to become
narrow inevitably in connection with this.

[0013] As a result, when the terminals 35 and 36 are arranged in series,
the gap between the terminals 35 and 36 becomes narrow, and there is
possibility of interference with the connection of the connectors 37 and
38, if for example, the gap between the cell connecting devices 39
provided with the connectors 37 and 38 cannot be maintained sufficiently,
and as a result, the cell connecting devices 39 come into contact with
each other, etc.

[0014] Moreover, since it is necessary to stack a lot of cells 31 in order
to obtain a required output in the case in which the fuel cell 30 is
mounted in a vehicle, if the terminals 35 and 36 are disposed on all of
the separators 33 and 34 of each cell 31, the weight will increase to an
extent that cannot be ignored because of the terminals 35 and 36, and the
cost will increase.

[0015] Next, cross sections of the principal part of a fuel cell and of a
voltage detecting connector which is connected to the fuel cell are shown
in FIG. 10, as is disclosed in, for example, the patent document 3
(Japanese Unexamined Patent Application, First Publication No.
2002-352820). As shown in this figure, a fuel cell 130 consists of a
predetermined number (in this case, n) of cells 131, which are stacked.
Each cell 131 is interposed between separators 133 and 134 in a membrane
electrode architecture 132. In each cell 131, a terminal 135 for
measuring electrical voltage is disposed on a separator 133 at an anode
electrode side. A cell connecting device 139 is connected to the fuel
cell 130 thus constituted. The cell connecting device 139 is equipped
with a predetermined number of connectors 137, whereby the electrical
voltage of the separators 133 disposed at the terminals 135 can be
detected by contacting the connectors 137 with the terminals 135, thereby
detecting electrical voltage in each cell.

[0016] However, there are the following problems in the prior art. That
is, hitherto, as explained referring to FIG. 10, because a terminal is
disposed on the separator of one electrode (for example, an anode
electrode), in order to detect the cell voltage of one cell, the
monitoring is performed ranging over the separator of the electrode
shared with the adjoining cell. As a result, in the case of detecting the
cell voltage of the end cell of a stacked body in which plural cells are
stacked, there is no cell adjoining thereto, and it is impossible to
detect the cell voltage of the end cell. Therefore, in order to detect
the cell voltage of the end cell, as shown in FIG. 10, it is necessary to
dispose a cover plate (dummy separator) 140 having the same shape as a
separator (separator at the side of an anode electrode) 134, on the end
of the stacked body of cells and to dispose a terminal 141 for a
connector 142 on the cover plate 140. Thus, it is necessary to dispose
separately, a separator, a terminal, and a connector, which are not
related to power generation, and the number of parts increases, thereby
increasing cost, stacking width, and weight.

SUMMARY OF THE INVENTION

[0017] Therefore, it is an object of the present invention to provide a
connecting structure to the cell of a voltage detecting connector which
can prevent increase in weight due to terminals and increase of cost,
while detecting all of the cell voltages and maintaining gaps between
terminals, and a fuel cell.

[0018] In addition, it is another object of the present invention to
provide a connecting structure to the cell of a voltage detecting
connector which can detect the cell voltage at both ends of the stacked
body, while prevent increase in the number of parts, cost, stacking
width, and weight, and a fuel cell.

[0019] The first aspect of the present invention is a connecting structure
between a connecting apparatus for a fuel cell and a fuel cell (for
example, a fuel cell 1, in the embodiment) having a structure in which
first cells (for example, first cells 2a in the embodiment) having
terminals (for example, terminals 6 and 7, in the embodiment) provided to
cathodes (for example, cathode electrodes 12, in the embodiment) and
anodes (for example, anode electrodes 11, in the embodiment) thereof, and
second cells (for example, second cells 2b, in the embodiment) having
terminals provides to neither cathodes nor anodes thereof are stacked in
alternation, characterized in that the connecting apparatus and the fuel
cell are electrically connected by contacting the terminals with the
connectors which are disposed at positions corresponding to the
terminals, in the connecting apparatus.

[0020] According to the first aspect of the present invention, since two
opposed electrodes of two cells adjoining in the stacking direction have
the same electric potential, the anodes or the cathodes of the second
cell in the fuel cell have the same electric potential as the anodes or
the cathodes of the first cells which adjoin the second cells in the
stacking direction. Therefore, since the voltage of the second cells with
no terminals can be obtained from the electric potential of the anodes or
the cathodes of the first cells which adjoin the second cells in the
stacking direction, it is possible to maintain high detecting accuracy
equivalent to the case in which terminals are disposed on the anodes and
the cathodes of all of the cells. Moreover, compared to the case in which
terminals are disposed on the anodes and the cathodes of all of the
cells, the total number of terminals can be reduced to be approximately
half, and hence, it is possible to maintain sufficient gaps between the
terminals, thereby enabling the connectors to be connected to the
terminals smoothly. In addition, it is possible to lower increase of
weight caused by the terminals as well as cost.

[0021] The second aspect of the present invention is a connecting
structure according to the first embodiment, in which the first cells are
disposed on at least both ends of the fuel cell, and the connectors are
connected to the fuel cell consisting of the first cells and the second
cells which are stacked alternately from both ends of the fuel cell.

[0022] According to the second aspect of the present invention, since the
first cells are disposed on both sides of the fuel cell, and the first
cells and the second cells are stacked alternately from both ends, it is
possible to know certainly the voltage of the first cells which are
disposed on both ends and the second cells which adjoin the first cells,
and as a result, it becomes possible to detect the voltage ranging over
all of the cells, while lowering increase of weight due to the terminals
and also cost, thereby maintaining the detecting accuracy of the cell
voltages to be equivalent to the case of disposing terminals to anodes
and cathodes of all of the cells. In addition, by disposing the cells
having terminals on both ends, it becomes unnecessary to use special
dummy cells.

[0023] The third aspect of the present invention is a fuel cell including:
first cells provided with terminals to each of anodes and cathodes
thereof, and second cells provided with no terminals to neither anodes
nor cathodes thereof, in which the first cells and the second cells are
stacked alternately.

[0024] According to the third aspect of the present invention, since the
voltage of the second cells with no terminals can be obtained from the
electric potential of the anodes or the cathodes of the first cells which
adjoin the second cells in the stacking direction, substantially all of
the cell voltages can be detected, and thereby it is possible to maintain
high detecting accuracy equivalent to the case of disposing terminals to
anodes and cathodes of all of the cells. Moreover, compared to the case
of disposing terminals to anodes and cathodes of all of the cells, the
total number of terminals can be reduced to be approximately half, and
hence, it is possible to maintain the gaps sufficiently between the
terminals, which enables the connectors to be connected to the terminals
smoothly. In addition, it is possible to lower increase of weight caused
by the terminals as well as cost.

[0025] The fourth aspect of the present invention is a fuel cell according
to the third aspect of the present invention, in which the first cells
are disposed to at least both ends in the direction of stacking, and the
first cell and the second cell are stacked alternately from both ends.

[0026] According to the fourth aspect of the present invention, since the
voltages of the first cell which are disposed to both ends and the second
cells which adjoin the first cells in the stacking direction can be
certainly known, it becomes possible to detect the voltages ranging over
all of the cells, while lowering increase of weight caused by the
terminals as well as cost, and as a result, it is possible to maintain
detecting accuracy at a level which is equivalent to the case of
disposing terminals to anodes and cathodes of all of cells. Moreover, by
disposing the cells with terminals on both ends, it becomes unnecessary
to use special dummy cells.

[0027] The fifth aspect of the present invention is a connecting structure
between a connecting apparatus for a fuel cell and a fuel cell (for
example, the fuel cell 1 in the embodiment) having a structure in which
first cells (for example, the first cell 2a in the embodiment) having
terminals (for example, the terminal 6 in the embodiment) provided only
to anodes (for example, an anode electrode 111) thereof, and second cells
having terminals provided only to cathodes (for example, the cathode
electrode 12 in the embodiment) thereof are stacked in alternation,
characterized in that the connecting apparatus and the fuel cell are
electrically connected by contacting the terminals with the connectors
(for example, the connectors 8 and 9 in the embodiment) which are
disposed at positions corresponding to the terminals, in the connecting
apparatus.

[0028] According to the fifth aspect of the present invention, since
mutually opposing electrodes of the cells adjoining each other in the
stacking direction have the same electrical potential, the anodes or the
cathodes of a cell have the same electrical potential as in the anodes or
the cathodes of the cells which oppose to the cell. Since only the first
cells which have terminals on the anodes only are stacked from the
anode-side end, the electrical potentials of the anodes of the first
cells which are detection targets can be obtained from the terminals
which are disposed on the anodes, whereas the electrical potentials of
the cathodes of the first cells can be obtained from the terminals which
are disposed on the anodes of the cells which adjoin the cells, and from
these the voltages of the first cells, which are detection targets, can
be obtained. On the other hand, since the second cells, which have a
terminal only at the cathode, are stacked from the cathode-side end, the
electrical potentials of the cathodes of the second cells which are
detection targets can be obtained from the terminals which are disposed
on the cathodes, whereas the electrical potential of the anodes of the
second cells can be obtained from the terminals which are disposed on the
cathodes of the cells which adjoin the cell, and from these the voltages
of the second cells, which are detection targets, can be obtained. Thus,
it is possible to detect the cell voltage at both ends, without disposing
parts which have nothing to do with electric generation, such as dummy
separators, terminals, and connectors to the end especially. Moreover, it
is possible to maintain high detecting accuracy which is approximately
equivalent to the case of disposing terminals to anodes and cathodes of
all of the cells, and to lower the total number of terminals to be
approximately half thereof, compared to the case of disposing terminals
to anodes and cathodes of all of the cells, and hence it becomes possible
to maintain the gaps between the terminals sufficiently, and thereby it
becomes possible to connect the connectors to the terminals smoothly. In
addition, it is possible to lower increase of weight caused by the
terminals as well as cost.

[0029] The sixth aspect of the present invention is the connecting
structure, according to the fifth aspect of the present invention, in
which the connectors are connected to terminals of a fuel cell including
a third cell (for example, the third cell 2c in the embodiment) provided
with no terminals at an anode and a cathode thereof, and the first cells
or the second cells which are stacked alternately.

[0030] According to the sixth aspect of the present invention, the third
cells are stacked alternately with the first cells or the second cells,
thereby it is possible to reduce the number of the terminals which are
disposed to a fuel cell, to lower increase of weight and cost, while
maintaining the necessary detecting accuracy.

[0031] The seventh aspect of the present invention is a fuel cell
including: first cells provided with terminals to each of anodes and
cathodes thereof, and second cells provided with no terminals to neither
anodes nor cathodes thereof, in which the first cells are stacked from an
end of an anode side in a stacking direction and the second cells are
stacked from an end of a cathode side in a stacking direction,
alternately.

[0032] According to the seventh aspect of the present invention, even if
the parts which have nothing to do with power generation, such as dummy
separators, terminals, and connectors are not disposed on the end
especially, the cell voltages of both ends can be detected. Moreover, it
is possible to maintain high detecting accuracy which is approximately
equivalent to the case of disposing terminals to anodes and cathodes of
all of the cells, and to lower the total number of terminals to be
approximately half, compared to the case of disposing terminals to anodes
and cathodes of all of the cells, and hence it becomes possible to
maintain the gaps between the terminals sufficiently, and thereby it
becomes possible to connect the connectors to the terminal smoothly. In
addition, it is possible to lower increase of weight caused by the
terminals as well as cost.

[0033] The eighth aspect of the present invention is the fuel cell
according to the seventh aspect of the present invention, in which the
third cells from neither anodes nor cathodes of which terminal are taken
out are stacked with the first cell or the second cell alternately.

[0034] According to the eight aspect of the present invention, it is
possible to reduce the number of the terminals which are disposed to a
fuel cell, to lower increase of weight and cost, while maintaining the
necessary detecting accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG. 1 is a sectional view of the principal part of a cell
connecting apparatus equipped with a fuel cell and a voltage detecting
connector connected to the fuel cell in one embodiment of the present
invention.

[0036] FIG. 2 is a schematic sectional view of a cell which constitutes a
fuel cell shown in FIG.1.

[0037] FIG. 3 is a plan view of the first cell shown in FIG. 1.

[0038] FIG. 4 is a perspective view of the principal part the fuel cell
shown in FIG. 1.

[0039] FIG. 5 is a sectional view of the principal part of a fuel cell and
a voltage detecting connector connected to the fuel cell in the above.

[0040] FIG. 6 is a sectional view of the principal part of a cell
connecting apparatus equipped with a fuel cell and a voltage detecting
connector connected to the fuel cell in another embodiment of the present
invention.

[0041] FIG. 7 is a schematic sectional view of a cell which constitutes a
fuel cell shown in FIG. 6.

[0042] FIG. 8 is a plan view of a first cell and of a second cell shown in
FIG.6.

[0043] FIG. 9 is a perspective view of the principal part the fuel cell
shown in FIG. 6.

[0044] FIG. 10 is a sectional view of the principal part of a fuel cell or
a voltage detecting connector connected to the fuel cell in the above.

DETAILED DESCRIPTION OF THE INVENTION

[0045] Hereinafter, the connecting structure to a cell of the voltage
detecting connector and fuel cell in one preferred embodiment of the
present invention will be explained with reference to drawings.

[0046] FIG. 1 is a sectional view of the principal part of a cell
connecting apparatus equipped with a fuel cell and a voltage detecting
connector connected to the fuel cell in one preferred embodiment of the
present invention. As shown in this figure, a fuel cell 1 is constituted
from a plurality of cells 2 which are stacked in a predetermined numbers
(in this case, n). Each cell 2 is constituted by sandwiching a membrane
electrode structure 3 with separators 4 and 5.

[0047] The fuel cell 1 in this embodiment is equipped with first cells 2a
(2) in which terminals 6 and 7 for measuring voltage are disposed on
separators 4 on anode electrode 11 sides (refer to FIG. 2) and separators
5 on cathode electrode 12 sides (refer to FIG. 2) respectively, and
second cells 2b (2) which have terminals 6 and 7 in neither the
separators 4 nor the separators 5.

[0048] The first cells 2a are disposed at both ends on a [+] polar side
and a [-] polar side, and first cells 2a and the second cells 2b are
alternately stacked from the both ends.

[0049] A cell connecting apparatus 10 is connected to the thus constituted
fuel cell 1. The cell connecting apparatus 10 is equipped with a
predetermined number of connectors 8 and 9, and can detect the voltage of
the first cells 2a to which terminals 6 and 7 are disposed, by contacting
the connectors 8 and 9 with the terminals 6 and 7 provided to the first
cells 2a, respectively. As to the detection of the voltages of the second
cells 2b, details will be mentioned later.

[0050] FIG. 2 is a schematic sectional view of a cell which constitutes
the fuel cell shown in FIG. 1. As shown in this figure, the membrane
electrode structure 3 is equipped with a solid polymer electrolyte
membrane 13, and an anode electrode 11 and a cathode electrode 12
disposed on either side thereof.

[0051] A ring-like sealing member 14 is set at the periphery of the
surface where a pair of the separators 4 and 5, which are disposed on
either side of the membrane electrode structure 3, are opposed to each
other, and the solid polymer electrolyte membrane 13 is sandwiched by the
sealing members 14. A fuel gas path 15, an oxidizing gas path 16, and a
cooling medium path 17 for supplying fuel gas, oxidizing gas, and a
cooling medium, respectively, are formed in both the separators 4 and 5.

[0052] FIG. 3 is a plan view of one of the first cells in this embodiment.
As shown in this figure, fuel gas penetrating holes 18a and 18b,
oxidizing gas penetrating holes 19a and 19b, and cooling medium
penetrating holes 20a and 20b are formed on both sides. In these
penetrating holes, those on one side (left side in the drawing) serve as
supplying ports 18a, 19a and 20a, whereas those on the other side (right
side in the drawing) serve as discharging ports 18b, 19b, and 20b. It
should be noted that the separator may be formed by cutting carbon etc.,
and may be formed by press molding a metal etc.

[0053] Moreover, the terminals 6 and 7 disposed on the separators 4 and 5
of the first cell 2a are, as shown in FIG. 4, formed at approximately the
same position, respectively, when they are looked at in the stacking
direction.

[0054] In the fuel cell 1 thus constituted, fuel gas (for example,
hydrogen gas) is supplied to the anode electrode 11 through the fuel gas
path 15, and oxidizing gas (for example, air containing oxygen) is
supplied to the cathode electrode 12 through the oxidizing gas path 16.
Then, hydrogen is ionized by the catalyst layer (not shown) of the anode
electrode 11, and it moves to the cathode electrode 12 side through the
solid polymer electrolyte membrane 13. The electrons generated at this
time are taken out to the external circuit, and used as electrical energy
in a direct current. At this time, hydrogen ions, electrons, and oxygen
react to produce water.

[0055] At this time, the electrodes which oppose to each other of the
cells 2a and 2b which adjoin each other in the stacking direction have
the same electrical potential. For example, as shown in FIG. 1, the
electrical potential Vk (1) of the cathode electrode 12 of the first cell
2a located at the first row of the end of the [+] polar side is
equivalent to the electrical potential Va (2) of the anode electrode 11
of the second cell 2b in the second row, which adjoins thereto.

[0056] In this way, the anode electrode 11 or the cathode electrode 12 of
the second cell 2b in the fuel cell 1 has an electrical potential
equivalent to that of the cathode electrode 12 or the anode electrode 11
of the first cell 2a which adjoins the second cell 2b in the stacking
direction.

[0057] For example, the voltage V(n-1) of the second cell 2b located in
the (n-1)st row on the [-] polar side can be obtained as the difference
between the electrical potential Va (n-1) of the anode electrode 11 of
the second cell 2b and the electrical potential Vk(n-1) of the cathode
electrode 12. And the electrical potential of the anode electrode 11 of
the second cell 2b is equivalent to that of the cathode electrode 12 of
the first cell 2a located at the (n-2)th row, and the electrical
potential of the cathode electrode 12 of the second cell 2b is equivalent
to that of the anode electrode 11 of the first cell 2a located at the nth
row. In other words, the electrical potential Va (n-1) is equivalent to
the electrical potential Vk (n-2), whereas the electrical potential Vk
(n-1) is equivalent to the electrical potential Va (n). Therefore, the
electrical potential V (n-1) of the second cell 2b can be obtained as the
difference between the electrical potential Vk (n-2) and the electrical
potential Va (n).

[0058] Therefore, the voltage of the second cell 2b with no terminals 6
and 7 can be obtained from the electrical potential of the anode
electrode 11 or of the cathode electrode 12 of the first cell 2a which
adjoins the second cell 2b in the stacking direction.

[0059] Moreover, in the fuel cell 1 of this embodiment, the first cells 2a
are disposed at both ends of the [+] polar side and the [-] polar side,
and the first cells 2a and the second cells 2b are stacked from the both
ends alternately, and hence it is possible to know certainly the voltage
of the first cells 2a which are disposed at both ends and the second
cells 2b which adjoin the first cells 2a in the stacking direction.
Accordingly, substantially all of the cell voltages can be detected, and
as a result, it is possible to maintain high detecting accuracy
equivalent to the case of disposing the terminals 6 and 7 to the anode
electrodes 11 or the cathodes 12 of all of the cells 2. In particular,
when the total number of the cells is an odd number, it becomes possible
to detect all of the cell voltages by stacking the first cells and the
second cells alternately.

[0060] When the total number of the cells is an even number, the first
cells are stacked exclusively at the center position, and thereby all of
the cell voltages can be detected.

[0061] And since the total number of terminals 6 and 7 can be lowered to
be approximately half compared to the case of disposing terminals 6 and 7
to the anode electrodes 11 or the cathode electrodes 12 of all of the
cells 2, the gaps between the terminals 6 and 7 can be sufficiently
maintained, and it becomes possible to smoothly connect the connectors 8
and 9 to the terminals 6 and 7, respectively. Furthermore, cost can be
lowered while preventing weight increase caused by the terminals 6 and 7.

[0062] It should be noted that it is needless to say that the scope of the
present invention is not restricted only to the above embodiment. For
example, although in this embodiment it is explained taking the case in
which the first cells 2a which have terminals 6 and 7 are disposed at
both ends in the stacking direction, it is also possible to dispose the
second cells 2b at both ends.

[0063] In this case, it is necessary to insert a dummy separator into both
ends to detect the cell voltage of the cells at both ends. Moreover,
although the terminals 6 and 7 having a projected shape are formed
outside the end surfaces of the separators 4 and 5, respectively, to be
inserted into the connectors 8 and 9, respectively, it is also possible
to form terminals having a groove shape inside the end surfaces of the
separators 4 and 5 such that the connectors can be inserted thereto, and
further, the terminals may be formed integrally without changing the
outer shape of the separators 4 and 5.

[0064] Moreover, in this embodiment there is explained a case in which the
first cells and the second cells, which constitute the fuel cell, are
stacked alternately ranging over the entirety of the line, but what is
necessary is that at least the first cells and the second cells are
stacked alternately.

[0065] Hereinafter, the connecting structure to a cell of the voltage
detecting connector and the fuel cell in another preferred embodiment of
the present invention will be explained with reference to the drawings.

[0066] FIG. 6 is a sectional view of the principal part of a cell
connecting apparatus equipped with a fuel cell and a voltage detecting
connector connected to the fuel cell in another preferred embodiment of
the present invention. As shown in this figure, a fuel cell 101 is
constituted from a plurality of cells 102 which are stacked in a
predetermined number (in this case, n) of cells 102. Each cell 102 is
constituted by sandwiching a membrane electrode structure 103 with
separators 104 and 105.

[0067] The fuel cell 101 in this embodiment is equipped with first cells
102a (102) in which the terminal 106 for measuring voltage is disposed on
a separator 104 on an anode electrode 211 side (refer to FIG. 7), second
cells 102b (102) in which the terminal 107 for measuring voltage is
disposed on a cathode electrode 112 side (refer to FIG. 7), and second
cells 102c (102) which have terminals 106 and 107 in neither,the
separator 104 nor the separator 105.

[0068] A first cell 102a is disposed at the end of a [+] polar side, and a
first cell 102b is disposed at the end of a [-] polar side, and the first
cells 102a and the third cells 102c are stacked alternately, the second
cells 102b and the third cells 102c are stacked alternately, from each
end.

[0069] A cell connecting apparatus 110 is connected to the thus
constituted fuel cell 101. The cell connecting apparatus 110 is equipped
with a predetermined number of connectors 108 and 109, and can detect the
voltages of the anode electrodes 111 of the first cells 102a and the
voltages of the cathode electrodes 112 of the second cells 102b, by
contacting the connectors 108 with the terminals 106 disposed on the
first cells 102a, and by contacting the connectors 109 with the terminals
107 provided on the second cells 102b, respectively.

[0070] FIG. 7 is a schematic sectional view of a cell which constitutes
the fuel cell shown in FIG. 6. As shown in this figure, the membrane
electrode structure 103 is equipped with a solid polymer electrolyte
membrane 113, and an anode electrode 111 and a cathode electrode 112
disposed on either side thereof.

[0071] A ring-like sealing member 114 is set on the periphery of the
surface where a pair of the separators 104 and 105, which are disposed on
both surfaces of the membrane electrode structure 103, oppose each other,
and the solid polymer electrolyte membrane 113 is sandwiched by the
sealing members 114. A fuel gas path 115, an oxidizing gas path 116, and
a cooling medium path 117 for supplying fuel gas, oxidizing gas, and a
cooling medium, respectively, are formed in both the separators 104 and
105.

[0072] FIG. 8 is a plan view of one of the first cells in this embodiment.
As shown in this figure, fuel gas penetrating holes 118a and 118b,
oxidizing gas penetrating holes 119a and 119b, and cooling medium
penetrating holes 120a and 120b are formed in both sides. In these
penetrating holes, those on one side (left side in the drawing) serve as
supplying ports 118a, 119a and 120a, whereas those on the other side
(right side in the drawing) serve as discharging ports 118b, 119b, and
120b. It should be noted that the separator may be formed by cutting
carbon etc., and may be formed by press molding a metal etc.

[0073] Moreover, the terminals 106 and 107 disposed on the separators 104
and 105 of the first cell 102a are, as shown in FIG. 9, formed at
approximately the same position, respectively, when they are looked at in
the stacking direction.

[0074] In the fuel cell 101 thus constituted, fuel gas (for example,
hydrogen gas) is supplied to the anode electrode 111 through the fuel gas
path 115, and oxidizing gas (for example, air containing oxygen) is
supplied to the cathode electrode 112 through the oxidizing gas path 116.
Then, hydrogen is ionized by the catalyst layer (not shown) of the anode
electrode 111, and it moves to the cathode electrode 112 side through the
solid polymer electrolyte membrane 113. The electrons generated at this
time are taken out to the external circuit, and used as electrical energy
in a direct current. At this time, hydrogen ions, electrons, and oxygen
react to produce water.

[0075] At this time, the electrodes which oppose each other of the cells
102a and 102b or of the cells 102b and 102c which adjoin each other in
the stacking direction have the same electrical potential. For example,
the electrical potential of the cathode electrode 112 of the first cell
102a located at the first row of the end of the [+] polar side is
equivalent to the electrical potential V of the anode electrode 111 of
the third cell 102c in the second row, which adjoins thereto. Moreover,
the electrical potential of the anode electrode 111 of the second cell
102b located at the nth row at the [-] polar side is equivalent to the
electrical potential of the anode electrode 112 of the third cell 102c
located in the (n-1)th row, which adjoins thereto.

[0076] In this embodiment, since the third cells 102c are stacked with the
first cells 102a or the second cells 102b alternately, it is possible to
obtain the electric potential difference between two cells which adjoin
each other (for example, the first cell 102a and the third cell 102c, or
the second cell 102b and the third cell 102c). Therefore, it becomes
unnecessary to dispose a dummy separator, a terminal, or a connector
especially, which is not related to power generation, and the cell
voltage of both ends can be detected, while lowering the number of parts,
cost, stacking width, and increase in weight.

[0077] Since the total number of terminals 106 and 107 can be lowered to
be approximately 1/4 compared with the case of disposing terminals 106
and 107 on the anode electrodes 111 or the cathode electrodes 112 of all
the cells 102, the gaps between the terminals 106 and 107 can be
sufficiently maintained, and it becomes possible to connect smoothly
connectors 108 and 109 to the terminals 106 and 107, respectively.
Furthermore, cost can be lowered while preventing the weight increase
caused by the terminals 106 and 107.

[0078] It should be noted that, needless to say, the scope of the present
invention is not restricted only to this embodiment. In this embodiment,
although there is explained a case in which the third cells are stacked
with the first cells or the second cells alternately, the number of the
third cells can be increased or decreased, corresponding to the required
detecting accuracy. For example, it is possible to constitute the fuel
cell from the first cells and the second cells, without using the third
cells. In this case, when the first cells are stacked from one end of the
fuel cell, whereas only the second cells are stacked from the other end
of the fuel cell, it is possible to detect all of the cells by disposing
cells which are equipped with terminals at both the anode and the cathode
thereof at the center portion. Moreover, although the terminals 106 and
107 having a projected shape are formed outside the end surfaces of the
separators 104 and 105, respectively, to be inserted into the connectors
108 and 109, respectively, it is also possible to form terminals having a
groove shape inside the end surfaces of the separators 104 and 105 such
that the connectors can be inserted thereto, and further, the terminals
may be formed integrally without changing the outer shape of the
separators 104 and 105.

[0079] According to the first aspect or the third aspect of the present
invention, while detecting substantially all of the cell voltages, the
gap between terminals is maintained, thereby preventing weight increase
caused by the terminals, and increase in cost.

[0080] According to the second aspect or the fourth aspect of the present
invention, the detecting accuracy of the cell voltage can be maintained
at a level equivalent to the case of disposing terminals to the anodes
and the cathodes of all cells. Moreover, it becomes unnecessary to
dispose things like a special dummy cell by disposing the cell which has
terminals at both ends thereof.

[0081] According to the fifth aspect or the eighth aspect of the present
invention, the cell voltages of both ends can be detected, while lowering
the number of parts, cost, stacking width and increase in weight.

[0082] According to the sixth aspect or the seventh aspect of the present
invention, while maintaining the detection accuracy required, the number
of terminals which are disposed on a fuel cell can be reduced further,
thereby lowering the increase in weight and cost further.